Albert Einstein once said, "If at first, the idea is not absurd, then
there is no hope for it".

Andres

On Thu, 24 Mar 2005 12:24:33 +0000, Adrian Bowyer <A.Bowyer@bath.ac.uk>
wrote:
>
> Bathsheba Grossman wrote:
>
> > That's not exactly my experience of how tolerance failures tend to
> > work; I doubt it's a general principle that they fall on a bell
curve.
> > If they did, a complex part might have 20 dimensions, and if one of
> > them happens to be right, you'd still rolling the dice on the other
> > 19.
> >
> > I'd bet a dollar that the author of that paper has never operated a
> > milling machine. A vertical mill with all the trimmings is the
> > closest thing I can think of to a large-scale self-replicating
> > machine, and think about what would happen if you took a Harbor
> > Freight mill and tried to make another one.
>
> Not only do I operate one, I own one. It's in my workshop at home.
> In all this talk of accuracy, remember this: people have been making
objects
> accurate to within the wavelength of light since medieval times using
nothing
> fancier than a knife edge and a candle...
>
> > There are only a few types of self-replicating machine in the known
> > universe, all biomolecular: DNA-based life, RNA-based machines
> > contingent on the "RNA world" hypothesis proving out, and parasitic
> > prions if the "protein-only" hypothesis is true.
> >
> > If I were building such a machine, I'd be looking very hard at the
way
> > analog and digital mechanisms interact in those systems. There's an
> > entropic principle that has to be overcome, and the way DNA does it
is
> > an awesome hack; any other such machine would have to be built
around
> > an equally awesome hack. DNA relies on the uniform nature of
> > elementary particles, and therefore its existence may not imply a
> > useful model for larger scales. If this problem did turn out to be
> > soluble on the macro scale, that would have consequences far beyond
> > having cheap SLA in every household.
>
> Hmmm. Doesn't human engineering as a whole also constitute a
self-replicating
> machine?
>
> Yours
>
> Adrian
>
> http://staff.bath.ac.uk/ensab>
>